Apparatus for recovering volatilizable metals



Nov. 14, 1944. M HDGEON 2,362,718

APPARATUS FOR RECOVERING VOLATILIZABLE METALS 2 Sheets-Sheet 1 Filed June 4. 1942 IIVVENTO P: LL 0Y0 M P/DGEU/f/ ATTOR/VEM Patented Nov. 14, 1944 APPARATUS FOR necovmmo vom'rmz- ABLE METALS Lloyd Montgomery Pidgeon, Rookclill'e Park,

Ontario, Canada, assignor, by mesne assiznments, to Dominion Mmesium Limited, gm, Ontario, Canada, a corporation of Application June 4, 1942, Serial No. 445,714

' In Canada May 20, 1942 8 Claims. (Cl. 13--8) This invention relates to' a means for extractshowing an alternative arrangement 0! heatinlt lug volatilizable metals such as magnesium and means, the like from materials containing the same. Figure 4 is a fragmentary view in side eleva- The reactions which occur in the extraction tion of the arrangement shown in Figure 3, and cl such. metals are usually endothermic and rea Figure 5 is a sectional elevation of another versilcle. At any given temperature equilibrium form of furnace. may be readily established, as a result of which Referring to Figure l of the drawings, l is a the reset-lo? 3 will not proceed in either direction rectangular chamber of elongated shone giroec long lo various reactants, in the ecuillb vicling; e. vertically extending reaction zone, or concentration, remain in the system i. column l, having reimctory lining the reactions are carried out. is thus iormed, on opposite side w lls, c. :9 step to remove the volctlle reaction steps, shelves, or surfaces oi cl'll the system continucu ly end as which. dew? A *1 ed. will he le d that t cscr i step to h to overcome the e lent to the reaction to charge is usually a W "'lle ilt to achieve this.

us for produc vet " l'eliiuction e.- chmige of h an elongated r wl'neil movement of ti passage through the charge during such vc iouriz'e the metal the ,wlt

. Whltfih will. o or of A n steps: the heating of the l provided adjacent the :cct contact with the heating ole freeing the material should it join. he eloved, the passing of an inert gas lhl'oullh the shown, the poker may he permanently mounted some to remove metal vapours, the condensing of in the furnace wall, a packing gland i! being the vapours outside the reaction zone, and the provided to prevent escape of hot gases from the maintaining of a continuous reaction process in furnace. the zone while continuously or intermittently 45 Means for providing a continuous flow of an feeding a charge thereto and discharging r sid inert gas, such as hydrogen, through the furnace, therefrom. comprises an inlet pipe 16, having va1ve-con- The invention will be described with particular trolled branches l6 leading to the hoppers i3 reference to the accompanying drawings in and M to pass the gas in countercurrent to the whim 5o charge, and an inlet pipe i1, having valve-con- Figure 1 is a sectional elevation of an appartrolled branches ll, leading to hoppers l and tuslnaccordance with the invention, 1 to pass inert gas downwardly with the charge.

Figure 2 is an elevation of a furnace with a A condenser i8 communicates with the furmg form of begun memm. nace interior at l9 and has an outlet 20 for Figure 3 is a sectional elevation or a furnace 55 the inert gas.

In operation, the briquetted charge consisting of magnesia containing material and ferrosilicon, or other reducing agents which produce non-gaseous oxidation products, is fed to the furnace and the residue discharged therefrom, as illustrated, in a continuous manner, the double feed and discharge hoppers constituting gas locks for the system. It will be observed that the briquettes, in their passage through the elongated reaction zone of the furnace, fall from one inclind shelf or came to another on the opposite wall, following a substantially zig-zag passage in which a rolling or mixing action is imparted to them, to cause repeated change in the port-ion of the charge exposed to direct heat radiation from the heating elements. This action substantially eliminates the possibility of localized overheating of any portion of the charge by the heating elements 4. The location of the latter adjacent the furnacawall away from the baffle edges also contributes to the avoidance of local overheating and to the protection of the elements from breakage since there is substantially no possibility of the briquettes coming into contact with them.

An inert gas, such as hydrogen, is passed upwardly through the reaction zone in a countercurrent to the movement of the heated charge, and, owing to the rolling movement of the briquettes, an efiective scouring of the reaction mixture is achieved, the metal vapours being swept into the condenser as they are formed. The downward flow of gas into the relatively cool portion of the charge prevents the rise therein of metal vapours. The distillate is indicated at All in the condenser.

The furnace may be operated at atmospheric pressure or under vacuum.

The elements 4 may extend through the furnace wall and be connected in series by the circuit 2 l, as shown in Figure 2.

An alternative manner of arranging the heating elements is illustrated in Figures 3 and 4. As shown, a row of elements 22 have only the end 23 of the top element and the end 24 of the bottom element extending through the wall of the furnace for connection to an electrical circuit 29, the other ends of elements being supported by columns 25 consisting of a series of blocks or bars positioned in recesses 23 in the furnace wall. The ends of the column consist of refractory supporting bars 38 and the remaining portion of each column consists of alternate bars 21 and 28 of a refractory material and a current-conducting material, such as graphite, respectively. It will thus be observed that current flows through one element 22, and the conducting bar 28 to the next element and thus throughout the furnace. One end of each column is resiliently supported by means of a spring 30 seated in a recessed casing 3| in the furnace wall, whereby the columns may be conveniently assembled and disassembled.

In Figure 5, there is illustrated a modification of the furnace shown in Figure 1 comprising a substantially cylindrical furnace 2| having annular baflles 33 and annular heating elements 34 arranged beneath the baffles therein. The baffles have a facing 35 of non-reactive material thereon. The inlet 36 and outlet 31 of the furnace may be provided with suitable feeding and discharge means.

It will be apparent that various other forms of furnace structures may be employed without departing from the spirit of the present invention. For instance, a spiral baffle formation may alternatively be employed in the cylindrical furnace shown in Figure 5.

Moreover, various other details of the structures described and illustrated may be altered while remaining within the scope of the invention. While the invention has been described with particular reference to the production of magnesium, it may be used for producing other volatilizable metals such as zinc and cadmium.

I claim:

1. Apparatus for extracting volatllizable metals from materials containing them comprising a furnace having an elongated vertically extending reaction zone therein, means for admitting materials to be treated at the top of said zone. a plurality of baffles carried by the furnace wall and extending into said zone, said baffles having inclined upper surfaces adapted to receive materials passing through the zone and to direct the same downwardly, and an exposed heating element located under each of said baflles out of contact with said materia1s, sald materials during their passage through said acne receiving direct radiant heat from said elements, and said bames imparting a rolling action to said materials to constantly change the surface thereof exposed to said radiant heat.

2. Apparatus for extracting volatlllzable metals from materials containing them comprising a furnace having an elongated vertically extending reaction none, means for admitting materials to be treated at the top of said zone, said materials being adapted to pass by gravity through the zone, baflles carried by the furnace wall and extending into the path of materials in the zone, said baffles having inclined upper surfaces adapt,- ed to direct the materials downwardly, exposed heating elements beneath said baffles and lying outside the path of travel of the materials, said materials during their passage through said zone receiving direct radiant heat from said elements. and said ballles imparting a rolling action to said materials to constantly change the surface thereof exposed to said radiant heat, means for discharging residue from the bottom of said zone,

and means for providing a continuous flow of an inert gas through said zone in counter-current to the direction of travel of the materials.

3. Apparatus for extracting volatlllzable metals from materials containing them as defined in claim 2, said banle upper surfaces having thereon a facing 01' a material nonreactive to the materials under treatment.

4. Apparatus for extracting volatillzable metals from materials containing them comprising a furnace having an elongated vertically extending reaction zone, means for admitting materials to be treated at the top of said zone, said materials being adapted to pass by gravity through the zone, bames carried by the furnace wall and extending into the path of travel of materials in the zone, said baffles having inclined upper surfaces adapted to direct the materials downwardly, exposed heating elements beneath the homes and lying outside said path of travel, sold materials during their passage through said zone receiving direct radiant heat from said elements. and said baflles importing a rolling action to said materials to constantly change the surface thereof exposed to said radiant heat, a condenser outside the reaction zone and having communication therewith. and means for sweeping metallic va'-.,

pours from said zone to said condenser.

tion. comprising a furnace having an elongated vertically extending reaction zone, means for admitting materials to be treated at the top of said zone, said materials being adapted to pass by gravity through the zone, a series of baiiles on each of two opposed walls of said furnace and each extending into the path of travel of materials in the zone, the bailies on one wall being in staggered relation to the bailies on the opposing wall. each baflie having an inclined upper surface adapted to direct the materials downwardly, and an exposed electrical resistance heating element extending beneath each baflie and lying outside the path of travel of the materials. said materials during their passage through said zone receiving direct radiant heat from said elements, and said bames imparting a rolling action to said materials to constantly change the surface thereof exposed to said radiant heat.

6. Apparatus for extracting volatilizable metals from materials containing them as deilned in claim 5, wherein the ends of said heating elements extend through the furnace wall and including an electrical circuit connecting said endsinaeries.

7. Apparatus for extracting volatilizable metals from materials containing them as defined in claim 5, including a pair of columns in said furnace ensasin and supp rting the ends of said heating elements, said columns consistin of alternate bars of electrical conducting and non-conducting materials. i

8. Apparatus for extracting .volatilizable metals from materials containing them comprising a furnace having an elongated substantially dylindrical reaction-zone therein, means for admitting materials to lie-treated at the top oflsald zone, said materials being adapted to pass by gravity through the zone, a series of annular baiiies carried by the furnace wall and extending into the path of travel of materials in the zone. said baiiies having inclined upper surfaces adapted to direct the materials downwardly, and an exposed annular heating element located beneath each baiile and lying outside the path of travel of the materials, said materials during their passage through said zone receiving direct radiant heat fromsaid elements, and said bames imparting a rolling action to said materials to constantly change the surface thereof exposed to said radiant heat.

LLOYD MONTGOMERY PIDGEON. 

